Blind estimation of amplitudes, phases, time delays and frequency offsets in multiple-access systems with circular transmissions

The problem of blind parameter estimation in multiple-access communication systems with circular transmissions is addressed. A non-data aided algorithm based on the higher-order cyclostationarity features of the received signal is proposed to estimate amplitude, phase, time delay, and frequency shift of each user.Furthermore, a reduced-complexity version of the algorithm is proposed whose computational cost is comparable with that of the second-order statistic based techniques. Simulation results are presented to show the effectiveness of the proposed algorithm to properly operate in severe noise and interference environments.